The Project is intended to shed further light on the nature of intra-individual change in intelligence in the elderly. Although this topic is probably the most heavily researched in the psychology of aging, controversies remain. There is a clear need to replicate the small number of sequential studies using multivariate measures with a view toward achieving a better level of consensus as to the course of intellectual change and the role of cohort differences within the elderly. Longitudinal follow-up testing will be attempted on an original sample of 1,116 persons recruited in cooperation with the American Association of Retired Persons who were tested originally in 1976-7 in 29 cities throughout the state of Florida. Data were gathered on an extensive battery of tests of intellectual functioning. Retest data will be used to evaluate hypotheses regarding the stability of factor structure, age changes and cohort differences in factor means and the role of variables believed to influence intellectual performance such as subjective health ratings, educational attainment and sex. These issues are to be studied through applications of restricted factor analysis and linear structural equation models. Further, identification of deceased individuals will allow for reanalyses of the initial data to evaluate hypotheses regarding eminence of death and intellectual performance. Replication is a central feature of scientific understanding. The view taken here is that current controversies with regard to intellectual functioning in the elderly are not likely to be resolved until further replications of the small number of previous sequential studies are completed. Desirable features of the current proposal include the unusually large initial sample and the very extensive battery of intellectual ability test employed.